Phytotoxic effect of plant extracts on physiology of cotton (Gossypium hirsutum L.) plants

Background: Plant-derived compounds are alternatives of synthetic insecticides in sustainable agriculture. Objective: This study investigated the phytotoxic effect of higher concentrations (2, 4, 8 and 16%) of four plants extracts (Azadirachta indica, Mentha arvensis, D. stramonium and Citrus limonium) on cotton plants. Methods: Each concentration was replicated four times to check the phytotoxic effect (CO2-in, CO2-out, H2O-in, H2O-out and photosynthesis absorption rate (PAR) in randomized complete block design. Data was recorded after 12, 24, 48 and 72 hours of spray with the help of Photosynthetic CL 340 meter. Results: The results showed that CO2-in was more affected by the D. stramonium (131.65 +/- 0.38) at 8% concentration. The overall progress showed that C. limonium was more affected the CO2-in of cotton crop. CO2-out was less affected by the C. limonium (117.83 +/- 1.46) at 4% concentration than M. arvensis (116.99 +/- 1.25) at 8% concentration and D. stramonium (115.77 +/- 0.74) at 16% concentration, but was more affected by the A. indica (118.15 +/- 0.71) at 4%. H2O-in was more affected by the C. limonium (0.39 +/- 0.05) than D. stramonium, A. indica and M. arvensis at 16% concentration. H2O-out of cotton was least affected by the D. stramonium (7.63 +/- 0.01) at 2% and more affected by the C. limonium (1.56 +/- 0.15) at 16% concentration. PAR was more affected by the A. indica (931.47 +/- 8.39) at 4% concentration and least affected by the M. arvensis (1499.7 +/- 9.94) at 8% concentration. Conclusions: Different dosages of various botanicals influenced the opening and closing of stomata and photosynthesis of cotton plants.